Sutro Biopharma Advances Three ADC Programs Toward Clinic Using Cell-Free Conjugation Platform

Sutro Biopharma's cell-free protein synthesis platform is moving from a manufacturing differentiator into a clinical proof point, with three site-specific ADC programs now at or approaching Phase 1 and a collaboration milestone triggered under its Astellas partnership. For CDMOs and plant heads evaluating next-generation bioconjugation capabilities, the cadence of IND-stage entries signals that cell-free, cell-free-enabled DAR-defined conjugation is graduating from platform narrative to reproducible process.

STRO-004, a DAR8 exatecan ADC targeting Tissue Factor, continues dose optimization in backfill cohorts within the ongoing STRIVE-01 Phase 1 study. Initial data from 49 heavily pretreated patients, reported in August 2026, showed confirmed and unconfirmed partial responses across three tumor types with a differentiated pharmacokinetic profile. Expansion cohort initiation and the next clinical data update are both planned for the first half of 2027.

STRO-006, a DAR8 exatecan ADC targeting integrin β6 (ITGB6), dosed its first patient in October 2026 in an open-label, multicenter Phase 1 study. The dose-escalation arm is enrolling patients with ITGB6-expressing tumors across seven indications, starting at 1.5 mg/kg, with an initial data readout expected in the second half of 2027. The program's selectivity profile reflects the precision conjugation control that Sutro's cell-free system is designed to enable at scale.

STRO-227, a DAR10 dual-payload ADC targeting PTK7, combines MMAE (DAR2) and exatecan (DAR8) within a single molecule to engage complementary mechanisms of action. Phase 1 initiation is targeted for early 2027. The dual-payload architecture is technically demanding from a bioconjugation standpoint; Sutro's ability to define discrete drug-to-antibody ratios for two distinct payloads in one construct is the manufacturing capability that underpins the program's design rationale.

On the collaboration side, Astellas dosed the first patient in its second dual-payload immunostimulatory ADC program, triggering a milestone payment to Sutro. Two Astellas programs are now active in the clinic under the partnership, which is focused on dual-payload iADC formats. Sutro reported $142.2 million in cash, cash equivalents, and marketable securities as of September 30, 2026, with runway projected into the first half of 2028.

The expansion cohort initiation for STRO-004 in the first half of 2027 will be the nearest-term indicator of whether the platform's conjugation consistency translates into the dose-exposure relationships required to support a pivotal program design.

Source: Sutro Biopharma, Inc. press release via GlobeNewswire, November 12, 2026.